Everyone needs to be aware of the PAYFORIT scam aided and abetted by giffgaff
I share your anger at GiffGaff's refusal to do anything to protect customers from these scams. Why won't they provide protection? Incompetence or greed (or maybe a bit of both!)
There are things consumers can do to fight back. You are entitled to assist on a FULL refund from the 'service provider'. In order to keep your money they have to prove that you consented to the charges. This is impossible for them to do. If a refund is not provided, use the Small Claims procedure if the company is based in the UK. If the 'service provider' is ovrseas, pursue the Level1 provider (Tap2Bill or similar company) for your refund. Again use the Small Claims procedure if necessary.
There is hope on the horizon with a review of these services by the regulator. There is a general expectation that some action will be taken following this, though I'm not sure it will be enough.
More detailed advice for dealing with 'Payforit' scams is i the faq linked in my signature.